GPGME

GnuPG Made Easy (GPGME) is a library designed to make
access to GnuPG easier for applications. It provides a
High-Level Crypto API for encryption, decryption, signing,
signature verification and key management. Currently it uses
GnuPG as its backend but the API isn't restricted to this
engine; in fact we have already developed a backend for CMS
(S/MIME).

Because the direct use of GnuPG from an application can be a
complicated programming task, it is suggested that all software
should try to use GPGME instead. This way bug fixes or
improvements can be done at a central place and every
application benefits from this.

Especially authors of MUAs should consider to use GPGME. It is
even planned to create a set of standard widgets for common key
selection tasks.